High-strength copper alloy plate excellent in oxide film adhesiveness

ABSTRACT

The present invention is a Cu—Fe—P system copper alloy plate comprising Fe: 0.02-0.5% and P: 0.01-0.25% in mass % with the balance consisting of copper and unavoidable impurities and having the ratio Fe/P of Fe to P in mass % being 2.0 to 5.0, wherein: a ratio of the area of fine crystal grains less than 0.5 μm in equivalent circle diameter to an observation area when a surface is observed by EBSD analysis is 0.90 or less; and the ratio C1s/Cu2p of a peak area of C1s to a peak area of Cu2p on the surface by XPS analysis is 0.35 or less.

FIELD OF THE INVENTION

The present invention relates to a copper alloy plate of a Cu—Fe—Psystem having an improved oxide film adhesiveness.

BACKGROUND OF THE INVENTION

The explanations are hereunder made on the basis of the case of using acopper alloy plate for a lead frame that is a semiconductor component asa representative application example of a copper alloy plate accordingto the present invention.

As a copper alloy for a semiconductor lead frame, a copper alloy of aCu—Fe—P system containing Fe and P is generally used.

Meanwhile, as a plastic package for a semiconductor device, a package ofsealing a semiconductor chip with a thermosetting resin is themainstream.

There are however the problems of package cracking and peel off causedduring implementation and use.

Here, the above problems are caused by poor adhesiveness between a resinand a lead frame. A substance most influencing the adhesiveness is anoxide film of a lead frame base material. An oxide film of several tento several hundred nanometers in thickness is formed on the surface of abase material during various heating processes for manufacturing a leadframe and a copper alloy and a resin touch each other through the oxidefilm. The peel off of such an oxide film from a lead frame base materialdirectly leads to the peel off between a resin and the lead frame andthe adhesiveness between the lead frame and the resin deterioratesconsiderably.

The problems of package cracking and peel off therefore depend on theadhesiveness of such an oxide film to a lead frame base material.Consequently, in a copper alloy plate of a Cu—Fe—P system as a leadframe base material, an oxide film formed on a surface through variousheating processes is required to have a good adhesiveness.

To cope with the problems, JP-A No. 2008-45204 (hereunder referred to asPatent Literature 1) proposes a method of improving oxide filmadhesiveness by controlling a texture and an average crystal grain sizeon a copper alloy plate surface in a composition having a reduced Fecontent of 0.50 mass % or less. That is, in Patent Literature 1, anorientation distribution density of Brass orientation in a texturemeasured by a crystal orientation analysis method with an electronbackscatter diffraction pattern EBSP of a copper alloy plate surface is25% or more and an average crystal grain size is 6.0 μm or less.

Meanwhile, JP-A No. 2008-127606 (hereunder referred to as PatentLiterature 2) proposes a method of improving oxide film adhesiveness bycontrolling the roughness and conformation of a copper alloy platesurface in a composition having a reduced Fe content of 0.50 mass % orless likewise. That is, a center line average roughness Ra is 0.2 μm orless, a maximum height Rmax is 1.5 μm or less, and a kurtosis (degree ofsharpness) Rku in a roughness curve is 5.0 or less in surface roughnessmeasurement of a copper alloy plate surface.

With a Cu—Fe—P system copper alloy plate disclosed in Patent Literatures1 and 2 however, it is impossible to materialize a higher level of oxidefilm adhesiveness which has been desired in recent years.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a Cu—Fe—P system copperalloy plate having both a higher strength and a higher level of oxidefilm adhesiveness which has been desired in recent years in acomposition substantially having a reduced Fe content of 0.5 mass % orless.

In order to attain the above object, a high-strength copper alloy plateexcellent in oxide film adhesiveness according to the present inventionis characterized by the copper alloy plate comprising Fe: 0.02-0.5% andP: 0.01-0.25% in mass % with the balance consisting of copper andunavoidable impurities and having the ratio Fe/P of Fe to P in mass %being 2.0 to 5.0, wherein: a ratio of the area of fine crystal grainsless than 0.5 μm in equivalent circle diameter to an observation areawhen a surface is observed by electron backscatter diffraction analysisis 0.90 or less; and the ratio C1s/Cu2p of a peak area of C1s to a peakarea of Cu2p on the surface by XPS analysis is 0.35 or less.

In a high-strength copper alloy plate excellent in oxide filmadhesiveness stated above, C1s/Cu2p of a surface obtained by XPSanalysis means a relative C quantity on a copper alloy plate surface asit will be described later. In order to reduce C1s/Cu2p on a copperalloy plate surface to 0.35 or less, it is necessary to almostcompletely remove a C source unremovable by alkali cathode electrolyticcleaning from the surface of the copper alloy plate prior to the alkalicathode electrolytic cleaning that is generally applied as finish ofplating pretreatment or the like. In other words, by almost completelyremoving a C source unremovable by alkali cathode electrolytic cleaningfrom the surface of a copper alloy plate prior to the alkali cathodeelectrolytic cleaning, it is possible to obtain a copper alloy plateexcellent in oxide film adhesiveness wherein C1s/Cu2p on a surfaceobtained by XPS analysis is 0.35 or less after the alkali cathodeelectrolytic cleaning is applied.

A copper alloy plate according to the present invention has a highstrength equivalent to a conventional copper alloy plate described inPatent Literatures 1 and 2. Further, by regulating an area ratio of finecrystal grains when the surface of a copper alloy plate according to thepresent invention is observed by EBSD analysis and C1s/Cu2p of thesurface obtained by XPS analysis to 0.35 or less, it is possible tomaterialize a higher level of oxide film adhesiveness that has beendesired in recent years. As a result, the present invention makes itpossible to prevent package cracking and peel off and provide ahighly-reliable semiconductor device. Alkali cathode electrolyticcleaning is generally applied to a copper alloy plate as finish ofplating pretreatment or the like and, as long a C source unremovable byalkali cathode electrolytic cleaning is almost completely removed fromthe surface of a copper alloy plate prior to the alkali cathodeelectrolytic cleaning, it is possible to obtain a copper alloy plateexcellent in oxide film adhesiveness wherein C1s/Cu2p of the surfaceobtained by XPS analysis is 0.35 or less after the alkali cathodeelectrolytic cleaning is applied.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The significance of requirements and embodiments in a Cu—Fe—P systemcopper alloy plate according to the present invention for satisfyingcharacteristics necessary as a material for a semiconductor lead frameor the like are specifically explained hereunder.

[Component Composition of Copper Alloy Plate]

In the present invention, in order to attain both a high strength and anexcellent oxide film adhesiveness as a material for a semiconductor leadframe or the like, a Cu—Fe—P system copper alloy plate has a basiccomposition comprising Fe: 0.02-0.5% and P: 0.01-0.25% in mass % and theratio Fe/P of Fe to P in mass % being 2.0 to 5.0, with the balanceconsisting of Cu and unavoidable impurities.

An embodiment further containing one or two kinds of Sn and Zn in theranges described below in the basic composition may also be allowable.Further, other unavoidable impurity elements are also allowed to becontained within ranges not hindering the characteristics. Here, %representing the contents of alloy elements and unavoidable impurityelements means mass % in all cases.

(Fe)

Fe is a major element that precipitates as Fe or an Fe-baseintermetallic compound and improves the strength and heat resistance ofa copper alloy. When an Fe content is less than 0.02%, the quantity ofprecipitated particles is small, the contribution to the improvement ofstrength is insufficient, and thus strength is insufficient. On theother hand, when an Fe content exceeds 0.5%, coarsecrystallized/precipitated particles tend to be generated, etchingproperty (smoothness of an etched face) and plating property (smoothnessof Ag plating and the like) deteriorate, and the contribution to theimprovement of strength is saturated. Consequently, an Fe content is setin the range of 0.02-0.5%, desirably 0.04-0.4%, and more desirably0.06-0.35%.

(P)

P has deoxidation function and is a major element that forms a compoundwith Fe and improves the strength and heat resistance of a copper alloy.When a P content is less than 0.01%, the precipitation of a compound isinsufficient and hence a desired strength cannot be obtained. On theother hand, when a P content exceeds 0.25%, hot workability and oxidefilm adhesiveness deteriorate. Consequently, a P content is set in therange of 0.01-0.25%, desirably 0.015-0.2%, and more desirably0.02-0.15%.

(Fe/P)

The regulation of Fe/P as a ratio of Fe to P in mass % is a regulationnecessary for efficiently precipitating a fine compound of Fe and Pcontributing to strength. When Fe/P is less than 2.0, the mass % of P isexcessively higher than the mass % of Fe, hence the quantity of agenerated fine Fe—P compound contributing to strength is insufficient, Pin a solid solution state remains abundantly, and strength and theadhesiveness of an oxide film deteriorate. On the other hand, when Fe/Pexceeds 5.0, the mass % of P is excessively lower than the mass % of Fe,hence likewise the quantity of a generated fine Fe—P compoundcontributing to strength is insufficient, Fe in a solid solution stateremains abundantly, and strength and the adhesiveness of an oxide filmdeteriorate. Consequently, Fe/P is set in the range of 2.0-5.0,desirably 2.2-4.7, and more desirably 2.4-4.4.

(Sn)

Sn contributes to the improvement of the strength of a copper alloy.When an Sn content is less than 0.005%, Sn does not contribute tostrengthening. On the other hand, when Sn is excessively contained inexcess of 3%, the solid solution quantity of Fe or an Fe—P compoundreduces, coarse crystallized/precipitated particles of Fe or an Fe—Pcompound tend to be generated, the effect of improving strengthdecreases, and hot workability and oxide film adhesiveness deteriorate.Consequently, a content of Sn selectively contained is selected from therange of 0.005-3%, desirably 0.008-2.7%, and more desirably 0.01-2.4% inaccordance with the balance between strength and oxide film adhesivenessrequired for application.

(Zn)

Zn improves the thermal peel resistance of solder in a copper alloy andSn plating necessary for a lead frame or the like, further improvesoxide film adhesiveness, and contributes to the improvement of thestrength of the copper alloy. When a Zn content is less than 0.005%,desired effects are not obtained. On the other hand, when a Zn contentexceeds 3%, the solid solution quantity of Fe or an Fe—P compoundreduces, coarse crystallized/precipitated particles of Fe or an Fe—Pcompound tend to be generated, the effect of improving strengthdecreases, and hot workability deteriorates. Further, the effect ofimproving oxide film adhesiveness is saturated. Consequently, a contentof Zn selectively contained is selected from the range of 0.005-3%,desirably 0.008-2.7%, and more desirably 0.01-2.4% in consideration ofstrength and oxide film adhesiveness required for application.

(Unavoidable impurities)

Unavoidable impurities referred to in the present invention are elementssuch as Mn, Mg, Ca, Zr, Ag, Cr, Cd, Be, Ti, Co, Ni, Au, and Pt forexample. When such an element is contained, coarsecrystallized/precipitated particles tend to be generated and strengthdeteriorates. Consequently, the total quantity of the elements isdesirably set at a least possible amount of 0.2 mass % or less. Further,elements such as Hf, Th, Li, Na, K, Sr, Pd, W, S, Si, C, Nb, Al, V, Y,Mo, Pb, In, Ga, Ge, As, Sb, Bi, Te, B, and misch metals contained in acopper alloy in minute amounts are also unavoidable impurities. Whensuch an element is contained, coarse crystallized/precipitated particlestend to be generated, hot workability deteriorates, and therefore thetotal quantity of the elements is desirably controlled to a leastpossible amount of 0.1 mass % or less. Further, O contained in a copperalloy in a minute amount oxidizes added elements, hence the quantity ofeffective added elements reduces, strength decreases, and therefore an Ocontent is desirably controlled to a least possible amount of 50 ppm orless in mass. Furthermore, H contained in a copper alloy in a minuteamount causes defects (blowholes and blisters) to be generated in thecopper alloy and hence an H content is desirably controlled to a leastpossible amount of 5 ppm or less in mass.

[Ratio of the Area of Fine Crystal Grains Less than 0.5 μm in EquivalentCircle Diameter to an Observation Area when a Surface is Observed byEBSD Analysis is 0.90 or Less]

A ratio of the area of fine crystal grains (less than 0.5 μm inequivalent circle diameter) to an observation area when the surface of acopper alloy plate is observed by EBSD analysis means, so to speak, aratio of the area occupied by fine crystal grains to a copper alloyplate surface. Here, EBSD analysis means electron backscatterdiffraction analysis and is a method of analyzing the distributions ofthe sizes and orientations of crystal grains. Here, a case where anorientation difference between adjacent measurement points is 5° or moreby EBSD analysis is regarded as a grain boundary and a crystal grainreferred to here is defined by a region completely surrounded by grainboundaries. An equivalent circle diameter referred to in the presentinvention is the diameter of a circle having an area identical to asurrounded region. The area ratio does not change between before andafter alkali cathode electrolytic cleaning.

The fact that the area ratio of fine crystal grains to a copper alloyplate surface is large means that many fine crystal grains exist andalso many crystal grain boundaries exist, defects caused by the crystalgrain boundaries are introduced abundantly in an oxide film, and theadhesiveness of the oxide film deteriorates. Consequently, the arearatio of fine crystal grains to a copper alloy plate surface should besmaller and is set at 0.90 or less, desirably 0.85 or less, and moredesirably 0.80 or less.

[Ratio C1s/Cu2p of a Peak Area of C1s to a Peak Area of Cu2p on aSurface By XPS Analysis is 0.35 or Less]

The ratio C1s/Cu2p of a peak area of C1s to a peak area of Cu2p on asurface by XPS analysis means, so to speak, a relative quantity of C ona copper alloy plate surface. XPS analysis means X-ray photoelectronspectrometry, is also called ESCA (Electron Spectroscopy for ChemicalAnalysis), and is an analysis method exceling at analyzing thecomposition and state of a very thin layer on a surface. C detected fromthe surface of a copper alloy plate is generally derived from variouscontaminants (organic and inorganic substances) and also derived from anorganic antirust film (of benzotriazole, etc.) applied for preventingthe discoloration of a copper alloy plate. The quantity of the C sourcesattaching to a copper alloy plate surface influences the magnitude ofC1s/Cu2p on the copper alloy plate surface. When the C sources exist ona copper alloy plate surface, the all C sources adversely affect theadhesiveness of an oxide film. This is presumably because an oxide filmhaving many defects tends to form by introducing defects caused by the Csources into the oxide film. Consequently, a value of C1s/Cu2p should besmaller and is set at 0.35 or less in the present invention, desirably0.30 or less, and more desirably 0.25 or less.

Meanwhile, a copper alloy plate used for a lead frame of a semiconductordevice is, after subjected to pretreatment including alkali cathodeelectrolytic cleaning, partially subjected to plating treatment such asAg plating and provided to an assembly process. The adhesiveness of anoxide film formed through the thermal history in the assembly processgoverns the reliability of a package. Consequently, a matter influencingthe adhesiveness of an oxide film is a C quantity after pretreatmentincluding alkali cathode electrolytic cleaning is applied to a copperalloy plate. The fact that a C quantity is large means that C sourcesunremovable by alkali cathode electrolytic cleaning adhere in quantityto a copper alloy plate surface prior to alkali cathode electrolyticcleaning. Here, an organic antirust film (of benzotriazole, etc.)generally used for preventing the discoloration of a copper alloy platecan be removed easily by alkali cathode electrolytic cleaning.

Here, alkali cathode electrolytic cleaning is a cleaning method ofapplying electrolysis with an object as a cathode in an alkaline aqueoussolution and enhancing detergency by mechanical stirring function of ahydrogen gas generated from the surface of the object and is a knowncleaning method in itself. An alkaline aqueous solution used in themethod is generally configured by using alkali salt such as sodiumhydroxide, sodium silicate, sodium phosphate, or sodium carbonate as thebase and adding an organic substance such as a surfactant or a chelatecompound, the electrolysis is carried out with an object as a cathode,hence the surface of a copper alloy plate is neither oxidized nordissolved, and not a damage is caused. Consequently, by using alkalicathode electrolytic cleaning, organic substances such as rolling oilused when a copper alloy plate is manufactured and an organic antirustfilm such as benzotriazole can be removed easily. Even by alkali cathodeelectrolytic cleaning however, organic substances (sticking substancesand the like) formed by transforming/degrading the rolling oil or thelike by heat or the like cannot be removed. When organic substances orthe like unremovable by such alkali cathode electrolytic cleaning adhereto the surface of a copper alloy plate prior to alkali cathodeelectrolytic cleaning, even after alkali cathode electrolytic cleaning,the organic substances remain on the copper alloy plate surface as Csources, the value of C1s/Cu2p on the copper alloy plate surfaceincreases, the adhesiveness of an oxide film deteriorates, and thereliability of a package also deteriorates. Consequently, it isimportant to remove C sources unremovable by alkali cathode electrolyticcleaning from the surface of a copper alloy plate beforehand at a stageprior to the alkali cathode electrolytic cleaning.

[Tensile Strength in the Longitudinal Direction is 500 MPa or More andPercentage Elongation after Fracture in the Longitudinal Direction is 5%or More]

In a copper alloy plate according to the present invention, preferablythe tensile strength in the longitudinal direction is 500 MPa or more asa measure of a high-strength material. Further, preferably thepercentage elongation after fracture in a tensile test in thelongitudinal direction is 5% or more. A copper alloy plate according tothe present invention: can maintain an appropriate bending workabilityrequired for a lead frame material by having an appropriate percentageelongation after fracture; and hence is a copper alloy plate suitable asa material of an electric/electronic component, in particular a materialof a lead frame for a semiconductor device. In contrast, when apercentage elongation after fracture in a tensile test in thelongitudinal direction is less than 5%, an appropriate bendingworkability required for a lead frame material cannot be maintained andhence such a copper alloy plate is not suitable as a material of anelectric/electronic component, in particular a material of a lead framefor a semiconductor device. Here, a percentage elongation after fractureof 5% or more can be obtained easily by a manufacturing method whichwill be described later as long as a copper alloy composition accordingto the present invention is adopted. Further, a tensile strength of 500MPa or more can also be obtained easily by a manufacturing method whichwill be described later except a region where an alloy element quantityis very small.

(Manufacturing Conditions)

Successively, manufacturing conditions desirable for making a copperalloy plate structure into a structure stipulated in the presentinvention are explained hereunder.

That is, firstly molten copper alloy adjusted to the above componentcomposition is cast. Then after the surface of a cast ingot is ground,the cast ingot is subjected to heating or homogenizing heat treatmentand successively hot-rolled, and the hot-rolled plate is water-cooled.Ordinary conditions may be applied in the hot rolling.

Successively, primary cold rolling called intermediate rolling isapplied, annealing and cleaning are applied, further thereafter finish(final) cold rolling and low temperature annealing (also called finalannealing, finish annealing, or stress relief annealing) are applied,and a copper alloy plate of a product thickness or the like is obtained.The annealing and cold rolling may be repeated. Here, qualityrequirements for the flatness of a plate and the reduction of internalstress come to be increasingly high in accordance with the finer wiringof a lead frame caused by the downsizing and higher integration of asemiconductor device and the low temperature annealing after finish coldrolling is effective for improving such quality. The thickness of aproduced copper alloy plate used for a semiconductor material such as alead frame is about 0.1 to 0.4 mm.

Here, solution treatment and quenching treatment by water cooling may beapplied to a copper alloy plate prior to the primary cold rolling. Onthis occasion, a solution treatment temperature is selected from therange of 750° C. to 1,000° C. for example. The final cold rolling isapplied also by an ordinary method.

In order to control a ratio of the area of fine crystal grains (lessthan 0.5 μm in equivalent circle diameter) to an observation area when acopper alloy plate surface is observed by EBSD analysis to 0.90 or lessand the ratio C1s/Cu2p of a peak area of C1s to a peak area of Cu2p on asurface by XPS analysis to 0.35 or less, the following processes may beadopted.

Firstly, in order to control a ratio of the area of fine crystal grains(less than 0.5 μm in equivalent circle diameter) to an observation areawhen a copper alloy plate surface is observed by EBSD analysis to 0.90or less, it is important to reduce the grain size of an abrasive andkeep the crystal grain size in the surface layer to a largest possibleextent by either not applying mechanical polishing after annealing orincreasing the grit number in mechanical polishing. Further, even whenmechanical polishing is applied, it is also an effective means to removea fine crystal layer generated in mechanical polishing by chemicaldissolution treatment, electrochemical dissolution treatment, or thelike after the mechanical polishing. Mechanical polishing has heretoforebeen applied after annealing in many cases. The reason is that an oxidefilm formed at annealing is robust and hardly removable only by acidcleaning in some cases. Consequently, in order to reduce the area ratioof fine crystal grains by either not applying mechanical polishing orreducing the load of mechanical polishing, it is important to control anannealing atmosphere sufficiently so as not to form a robust oxide film.Specifically, it is important to adopt a reduction atmosphere(atmosphere containing a reducible component such as H₂ or CO) as anannealing atmosphere and control an oxidizing component (O₂, H₂O, etc.)to a lowest possible concentration so as not to form a robust oxidefilm. In a low temperature annealing process as the final process inparticular, it is desirable to make an oxide film removable only by acidcleaning and not to apply mechanical polishing by controlling theannealing atmosphere sufficiently so as not to form a robust oxide film.

Successively, in order to control the ratio C1s/Cu2p of a peak area ofCis to a peak area of Cu2p on a copper alloy plate surface by XPSanalysis to 0.35 or less, it is important to apply cleaning treatmentbefore and after annealing. Although acid cleaning and polishing aregenerally applied after annealing in order to remove an oxide filmformed at the annealing and residues caused by rolling oil, it isparticularly difficult to effectively remove the residues caused byrolling oil only by cleaning after annealing, the residues remain on acopper alloy plate surface even after alkali cathode electrolyticcleaning as plating pretreatment is applied, the C quantity on thecopper alloy plate surface increases, and oxide film adhesivenessdeteriorates. Otherwise, if it is intended to sufficiently remove theresidues and the like caused by rolling oil only by cleaning afterannealing, the drawbacks of prolonging the time for cleaning andreducing the grit number of an abrasive (increasing the grain size of anadhesive) are caused. Here, if the grit number of an abrasive isreduced, fine crystal grains on a copper alloy plate surface increaseand coarsen and inversely oxide film adhesiveness is caused todeteriorate. Consequently, in order to effectively remove residues andthe like caused by rolling oil, it is effective to apply cleaningtreatment not only after annealing but also before annealing, it isparticularly essential to apply cleaning treatment before lowtemperature annealing as the final process and moreover it is effectiveto apply treatment for removing an oxide film by acid cleaning or thelike after low temperature annealing. As such cleaning treatment beforeannealing, there are various kinds of cleaning treatment such as solventcleaning, alkali cleaning, and alkali electrolytic cleaning and anappropriate cleaning method is used in accordance with need.

It is possible to reduce a C1s/Cu2p ratio on a surface by XPS analysisto 0.35 or less by further applying alkali cathode electrolytic cleaningto a copper alloy plate (prior to alkali cathode electrolytic cleaning)obtained by the above manufacturing method. The copper alloy plate isused for an electric/electronic component such as a semiconductor leadframe and, on that occasion, a C1s/Cu2p ratio on a plate surface reducesto 0.35 or less and an excellent oxide film adhesiveness can be obtainedby applying treatment including alkali cathode electrolytic cleaning aspretreatment of plating.

Example 1

Test results of Invention Examples and Comparative Examples forverifying the effects of the present invention are explained hereunder.As a manufacturing method of a copper alloy plate, firstly molten copperalloy is melted in a high-frequency furnace and successively casted intoa graphite-made book mold by tilt pouring. Thus ingots 50 mm inthickness, 200 mm in width, and 100 mm in length having the compositionsshown in Tables 1 and 2 are obtained.

Successively, a block 50 mm in thickness, 180 mm in width, and 80 mm inlength is cut out from each of the ingots, the rolled faces are ground,and the block is heated, retained for 0.5 to 1 hour after thetemperature has reached 950° C., hot-rolled until the thickness reaches16 mm, and water-cooled from a temperature of 700° C. or higher. Afterthe surfaces of the rolled plate are ground and oxide scale is removed,cold rolling and annealing are applied, successively final cold rollingis applied, and thus a copper alloy plate 0.2 mm in thickness isobtained. Low temperature annealing is applied after the final coldrolling. In the low temperature annealing, conditions allowing strengthnot to lower and enabling a braking elongation (percentage elongationafter fracture in tensile test in the longitudinal direction) of 5% ormore to be secured are selected from the temperature range of about 200°C. to 500° C. and the time range of about 1 to 300 sec.

Here the annealing and the low temperature annealing are applied in anN₂+10% H₂ atmosphere (dew point: −20° C. or lower, O₂ concentration: 50ppm or less) and the cleaning treatment before and after annealing isapplied as follows. With regard to the annealing, ultrasonic cleaning(20 kHz, 1 min.) by hexane is applied before the annealing and, afterthe annealing, sulfuric acid cleaning (10% sulfuric acid, 10 sec.) andsuccessively mechanical polishing (#2400 waterproof abrasive paper) areapplied. With regard to the low temperature annealing, ultrasoniccleaning (20 kHz, 1 min.) by hexane is applied before the annealing and,after the low temperature annealing, only sulfuric acid cleaning (10%sulfuric acid, 10 sec.) is applied and mechanical polishing is notapplied.

Here, the component other than the described elements in each of thecopper alloys shown in Table 1 comprises Cu and, as other impurityelements, the elements such as Mn, Mg, Ca, Zr, Ag, Cr, Cd, Be, Ti, Co,Ni, Au, and Pt are 0.2 mass % or less in total and the elements such asHf, Th, Li, Na, K, Sr, Pd, W, S, Si, C, Nb, Al, V, Y, Mo, Pb, In, Ga,Ge, As, Sb, Bi, Te, B, and misch metals are 0.1 mass % or less in total.

With regard to each of the copper alloy plates obtained as stated above,a specimen is cut out from a copper alloy plate, characteristics of thespecimen such as the surface properties (a C1s/Cu2p ratio and an arearatio of fine crystal grains), mechanical properties (a tensile strengthand a percentage elongation after fracture), and an oxide filmadhesiveness retention temperature are evaluated. The results are shownin Tables 1 and 2 respectively. In Table 2, a composition or a componentratio deviating from claims 1 to 4 according to the present invention isrepresented by being underlined.

(Area Ratio of Fine Crystal Grains)

An area ratio of fine crystal grains is obtained by measuring anobservation area when a copper alloy plate surface is observed by EBSDanalysis and an area of fine crystal grains (less than 0.5 μm inequivalent circle diameter) and computing an area ratio of the finecrystal grains by the method described earlier.

(C1s/Cu2p Ratio)

A C1s/Cu2p ratio is computed by measuring a peak area of Cu2p and a peakarea of C1s on a surface by XPS analysis after alkali cathodeelectrolytic cleaning is applied to a copper alloy plate surface. Here,the alkali cathode electrolytic cleaning is applied with an aqueoussolution containing sodium hydroxide by 20 g/L under the conditions ofliquid temperature: 60° C., cathode current density: 5 A/dm², and time:30 sec.

(Mechanical Properties)

Mechanical properties are obtained by making a JIS-No. 5 test piece inthe longitudinal direction and measuring a tensile strength and apercentage elongation after fracture in tensile test.

(Oxide Film Adhesiveness Retention Temperature)

An oxide film adhesiveness retention temperature is obtained by applyingalkali cathode electrolytic cleaning to a copper alloy plate surface,further applying water washing, acid washing (10% sulfuric acid), waterwashing, and then drying in sequence, successively applying heating for5 and 10 min. at a prescribed temperature in the atmosphere, andsuccessively evaluating by peeling test with an adhesive tape. Thealkali cathode electrolytic cleaning is applied under the sameconditions as the alkali cathode electrolytic cleaning applied when aC1s/Cu2p ratio is measured. The peeling test with an adhesive tape iscarried out by a method of attaching a commercially available tape(mending tape made by Sumitomo 3M Limited) and peeling off the tape. Onthis occasion, evaluation is carried out by varying the heatingtemperature at the intervals of 10° C. and regarding the maximumtemperature at which an oxide film does not peel off as an oxide filmadhesiveness retention

TABLE 1 Oxide film adhesiveness Surface properties Mechanical propertiesretention temperature ° C. Chemical components Area ratio of TensilePercentage Heating Heating Fe P Sn Zn Fe/P C1 s/Cu2 p fine crystalstrength elongation time time No. Mass % Mass % Mass % Mass % RatioRatio grains MPa after fracture % 5 min. 10 min. Invention 1 0.03 0.013— — 2.3 0.20 0.54 410 7 440 390 Example 2 0.05 0.011 — — 4.6 0.17 0.56440 7 440 390 3 0.06 0.026 — — 2.3 0.22 0.53 460 6 430 380 4 0.10 0.023— — 4.4 0.18 0.51 510 7 440 390 5 0.10 0.031 — — 3.2 0.21 0.45 520 8 430380 5 0.11 0.050 — — 2.2 0.24 0.47 530 7 420 370 7 0.17 0.038 — — 4.50.19 0.50 560 7 430 380 8 0.23 0.090 — — 2.6 0.23 0.48 580 8 410 360 90.30 0.064 — — 4.7 0.16 0.51 600 7 420 370 10 0.30 0.110 — — 2.7 0.210.50 620 8 410 360 11 0.32 0.150 — — 2.1 0.18 0.52 630 8 400 350 12 0.450.100 — — 4.5 0.19 0.48 680 7 390 340 13 0.46 0.210 — — 2.2 0.20 0.49700 8 390 340 14 0.10 0.033  0.02 — 3.0 0.25 0.51 540 8 430 380 15 0.100.035 1.0 — 2.9 0.21 0.53 650 10 410 360 16 0.11 0.035 2.5 — 3.1 0.180.45 750 11 390 340 17 0.11 0.030 — 0.02 3.7 0.19 0.47 520 8 440 390 180.10 0.031 — 1.0 3.2 0.20 0.48 560 8 460 410 19 0.10 0.032 — 2.5 3.10.15 0.55 600 9 480 430 20 0.11 0.034 1.1 1.0 3.2 0.22 0.47 680 10 440390 21 0.30 0.105 1.0 1.1 2.9 0.23 0.44 750 10 420 370

TABLE 2 Oxide film adhesiveness Surface properties Mechanical propertiesretention temperature ° C. Chemical components Area ratio of TensilePercentage Heating Heating Fe P Sn Zn Fe/P C1 s/Cu2 p fine crystalstrength elongation time time No. Mass % Mass % Mass % Mass % RatioRatio grains MPa after fracture % 5 min. 10 min. Comparative 22  0.0250.015 — — 1.7 0.17 0.53 400 7 420 370 Example 23 0.03 0.008 — — 3.8 0.180.51 360 6 440 390 24 0.06 0.010 — — 6.0 0.21 0.50 420 7 430 380 25 0.090.016 — — 5.6 0.20 0.52 460 8 420 370 26 0.11 0.062 — — 1.8 0.22 0.49500 8 390 340 27 0.30 0.055 — — 5.5 0.19 0.48 580 7 400 350 28 0.290.160 — — 1.8 0.17 0.51 610 8 350 300 29 0.45 0.080 — — 5.6 0.20 0.54650 7 370 320 30 0.50 0.290 — — 1.7 0.17 0.47 680 8 310 260 31 0.560.160 — — 3.5 0.23 0.50 670 8 380 330 32 0.10 0.031 4.0 — 3.2 0.22 0.51770 11 370 320 33 0.11 0.033 — 4.0 3.3 0.18 0.48 580 9 480 430

As shown in Table 1, in the copper alloy plates (Invention Examples 1 to21) according to the present invention, Invention Examples 1 to 13satisfy the composition ranges of claims 1 and 2, Invention Examples 14to 16 satisfy the composition range of claim 3, and Invention Examples17 to 21 satisfy the composition range of claim 4. Further, InventionExamples 1 to 21 satisfy the surface properties (an area ratio of finecrystal grains and a C1s/Cu2p ratio) stipulated in claims 1 and 2. Inthis way, the copper alloy plates of Invention Examples 1 to 21 havegood characteristics of the oxide film adhesiveness retentiontemperatures being 390° C.×5 min. or more and 340° C.×10 min. or more.

Here, whereas the oxide film peel off temperature of Invention Example 9in Table 1 of Patent Literature 1 (JP-A No. 2008-45204) is 370° C.×5min. (360° C.×5 min. in terms of oxide film adhesiveness retentiontemperature), the oxide film adhesiveness retention temperatures ofInvention Examples 10 and 11 in Table 1 of the present applicationhaving similar compositions are 410° C. to 400° C.×5 min. and it isobvious that the oxide film adhesiveness further improves in comparisonwith Patent Literature 1. Further, whereas the oxide film peel offtemperature of Invention Example 6 in Table 2 of Patent Literature 2(JP-A No. 2008-127606) is 400° C.×5 min. (390° C.×5 min. in terms ofoxide film adhesiveness retention temperature), the oxide filmadhesiveness retention temperature of Invention Example 10 in Table 1 ofthe present application having a similar composition is 410° C.×5 min.and it is obvious that the oxide film adhesiveness further improves alsoin comparison with Patent Literature 2.

On the other hand, in Comparative Examples 22 to 33, the compositionsand/or component ratios of claims 1 to 4 are not satisfied as shown inTable 2. Consequently, as it will be individually explained below, atensile strength is inferior or an oxide film adhesiveness retentiontemperature is low in comparison with Invention Examples 1 to 21. InComparative Example 22, Fe/P is lower than the lower limit value, thequantity of the generated fine Fe—P compound contributing to strength isinsufficient, P in a solid solution state increases, and hence thetensile strength and the oxide film adhesiveness retention temperatureare low in comparison with Invention Example 1.

In Comparative Example 23, the P content is lower than the lower limitvalue, the quantity of the generated Fe—P compound is insufficient, andhence the tensile strength lowers in comparison with Invention Example1.

In Comparative Example 24, Fe/P exceeds the upper limit value, thequantity of the generated fine Fe—P compound contributing to strength isinsufficient, Fe in a solid solution state increases, and hence thetensile strength and the oxide film adhesiveness retention temperatureare low in comparison with Invention Example 2.

In Comparative Example 25 too, Fe/P exceeds the upper limit value, thequantity of the generated fine Fe—P compound contributing to strength isinsufficient, Fe in a solid solution state increases, and hence thetensile strength and the oxide film adhesiveness retention temperatureare low in comparison with Invention Example 4.

In Comparative Example 26, Fe/P is lower than the lower limit value, thequantity of the generated fine Fe—P compound contributing to strength isinsufficient, P in a solid solution state increases, and hence thetensile strength and the oxide film adhesiveness retention temperatureare low in comparison with Invention Example 6.

In Comparative Example 27, Fe/P exceeds the upper limit value, thequantity of the generated fine Fe—P compound contributing to strength isinsufficient, Fe in a solid solution state increases, and hence thetensile strength and the oxide film adhesiveness retention temperatureare low in comparison with Invention Example 9.

In Comparative Example 28, Fe/P is lower than the lower limit value, thequantity of the generated fine Fe—P compound contributing to strength isinsufficient, P in a solid solution state increases, and hence thetensile strength and the oxide film adhesiveness retention temperatureare low in comparison with Invention Example 11.

In Comparative Example 29, Fe/P exceeds the upper limit value, thequantity of the generated fine Fe—P compound contributing to strength isinsufficient, Fe in a solid solution state increases, and hence thetensile strength and the oxide film adhesiveness retention temperatureare low in comparison with Invention Example 12.

In Comparative Example 30, P exceeds the upper limit value and Fe/P islower than the lower limit value, the quantity of the generated fineFe—P compound contributing to strength is insufficient, P in a solidsolution state increases, and hence the tensile strength and the oxidefilm adhesiveness retention temperature are low in comparison withInvention Example 13.

In Comparative Example 31, the Fe content exceeds the upper limit value,coarse crystallized/precipitated particles tend to be generated, hencethe contribution to the improvement of strength is low, and the tensilestrength lowers in comparison with Invention Example 13.

In Comparative Example 32, the Sn content exceeds the upper limit value,coarse crystallized/precipitated particles tend to be generated, hencethe strength improvement effect is low, and the tensile strength isalmost saturated and the oxide film adhesiveness retention temperaturelowers in comparison with Invention Example 16.

In Comparative Example 33, the Zn content exceeds the upper limit value,coarse crystallized/precipitated particles tend to be generated, hencethe strength improvement effect is low, and the tensile strength lowersand the effect of improving the oxide film adhesiveness retentiontemperature is saturated in comparison with Invention Example 19.

Example 2

Test results on the relationship between surface properties (an arearatio of fine crystal grains and C1s/Cu2p) and an oxide filmadhesiveness retention temperature are explained hereunder. In Example2, copper alloy plates 0.2 mm in thickness are manufactured from theingots of Invention Examples 5, 10, and 21 in Table 1 through themethods and conditions similar to Example 1.

Here in Example 2, surface properties (an area ratio of fine crystalgrains and C1s/Cu2p) of a copper alloy plate are varied by changingcleaning methods before and after annealing. Successively, surfaceproperties (an area ratio of fine crystal grains and C1s/Cu2p) and anoxide film adhesiveness retention temperature are evaluated in the samemanner as Example 1.

The cleaning methods of the cases and the evaluation results of thesurface properties (an area ratio of fine crystal grains and C1s/Cu2p)and the oxide film adhesiveness retention temperatures are shown inTables 3 and 4. Copper alloy plates manufactured from the ingots used inInvention Example 5 in Table 1 are used in Invention Examples 5-1 to 5-3and Comparative Examples 5-4 and 5-5 in Tables 3 and 4, copper alloyplates manufactured from the ingots used in Invention Example 10 inTable 1 are used in Invention Example 10-1 and Comparative Examples 10-2and 10-3 in Tables 3 and 4, and copper alloy plates manufactured fromthe ingots used in Invention Example 21 in Table 1 are used in InventionExamples 21-1 to 21-5 and Comparative Examples 21-6 to 21-9 in Tables 3and 4. In Tables 3 and 4, in the alkali dip cleaning, a typicalcommercially-available alkali dip cleaning solvent agent containingsodium hydroxide as the main component, phosphoric salt, silicate salt,carbonate, and a surfactant is used. Further, in the chemicaldissolution treatment applied in the post-treatment of annealing, atypical commercially-available aqueous solution containing sulfuric acidand hydrogen peroxide as the main components is used. Here, the itemsdeviating from the scope of Claims in the column of the surfaceproperties in Table 4 are shown by being underlined.

TABLE 3 Oxide film adhesiveness Cleaning method before and afterannealing Surface properties retention temperature ° C. Before low Afterlow Area ratio of Heating Heating Before After temperature temperatureC1 s/Cu2 p fine crystal time time No. annealing annealing annealingannealing Ratio grains 5 min. 10 min. Invention  5-1 Hexane, Sulfuricacid Hexane, Sulfuric acid 0.30 0.73 410 360 Example dip →#600 Polishingdip  5-2 Hexane, Sulfuric acid Hexane, Sulfuric acid 0.21 0.45 430 380ultra- →#2400 Polishing ultrasonic sonic wave wave  5-3 Hexane, Sulfuricacid Hexane, Sulfuric acid 0.09 0.12 450 400 ultra- →#2400 Polishingultrasonic sonic →Chemical wave wave dissolution →Alkali dip 10-1Hexane, Sulfuric acid Hexane, Sulfuric acid 0.21 0.50 410 360 ultra-→#2400 Polishing ultrasonic sonic wave wave 21-1 Hexane, Sulfuric acidHexane, Sulfuric acid 0.31 0.72 400 350 dip →#600 Polishing dip 21-2Hexane, Sulfuric acid Hexane, Sulfuric acid 0.23 0.44 420 370 ultra-→#2400 Polishing ultrasonic sonic wave wave 21-3 Hexane, Sulfuric acidHexane, Sulfuric acid 0.10 0.11 440 390 ultra- →#2400 Polishingultrasonic sonic →Chemical wave wave dissolution →Alkali dip 21-4Hexane, Sulfuric acid Hexane, Sulfuric acid 0.12 0.68 420 370 ultra-→#600 Polishing ultrasonic wave sonic →Alkali dip wave 21-5 Hexane,Sulfuric acid Hexane, Sulfuric acid 0.29 0.10 420 370 dip →#2400Polishing dip →Chemical dissolution

TABLE 4 Oxide film adhesiveness Cleaning method before and afterannealing Surface properties retention temperature ° C. Before low Afterlow Area ratio of Heating Heating Before After temperature temperatureC1 s/Cu2 p fine crystal time time No. annealing annealing annealingannealing Ratio grains 5 min. 10 min. Comparative  5-4 Ethanol; Sulfuricacid Ethanol, Sulfuric acid 0.46 0.73 390 340 Example dip →#600Polishing dip  5-5 Ethanol, Sulfuric acid Ethanol, Sulfuric acid 0.480.98 370 320 dip →#600 Polishing dip →#600 Polishing 10-2 Ethanol,Sulfuric acid Ethanol, Sulfuric acid 0.45 0.72 370 320 dip →#600Polishing dip 10-3 Ethanol, Sulfuric acid Ethanol, Sulfuric acid 0.460.96 350 300 dip →#600 Polishing dip →#600 Polishing 21-6 Ethanol,Sulfuric acid Ethanol, Sulfuric acid 0.43 0.75 380 330 dip →#600Polishing dip 21-7 Ethanol, Sulfuric acid Ethanol, Sulfuric acid 0.450.97 360 310 dip →#600 Polishing dip →#600 Polishing 21-8 Hexane,Sulfuric acid Hexane, Sulfuric acid 0.30 0.97 380 330 dip →#600Polishing dip →#600 Polishing 21-9 Ethanol, Sulfuric acid Ethanol,Sulfuric acid 0.44 0.92 370 320 dip →#120 Polishing dip

As shown in Table 3, in the copper alloy plates (Invention Examples 5-1to 5-3, 10-1, and 21-1 to 21-5) according to the present invention,appropriate cleaning treatment is applied before and after both therespective annealing and low temperature annealing, hence C1s/Cu2p on asurface by XPS analysis after alkali cathode electrolytic cleaning isapplied to the surface of a copper alloy plate is as good as 0.35 orless, and the area ratio of fine crystal grains (less than 0.5 μm inequivalent circle diameter) to an observation area by EBSD analysis on acopper alloy plate surface is also as good as 0.90 or less. Here,Invention Example 5-2 is identical to Invention Example 5 in Table 1,Invention Example 10-1 is identical to Invention Example 10 in Table 1,and Invention Example 21-2 is identical to Invention Example 21 in Table1.

As a result, the oxide film adhesiveness retention temperatures of thecopper alloy plates (Invention Examples 5-1 to 5-3, 10-1, and 21-1 to21-5) according to the present invention are 400° C.×5 min. or more and350° C.×10 min. or more and show good characteristics. Further, whencompositions are identical, as C1s/Cu2p and the area ratio of finecrystal grains reduce, the oxide film adhesiveness retention temperatureimproves further.

In Comparative Example 5-4, ethanol showing a weak detergency to rollingoil and the like is used and also only dip cleaning is applied at thecleaning treatment before both the annealing and the low temperatureannealing, and hence C1s/Cu2p exceeds the upper limit value and theoxide film adhesiveness retention temperature is low in comparison withInvention Example 5-1.

In Comparative Example 5-5, likewise ethanol showing a weak detergencyto rolling oil and the like is used and also only dip cleaning isapplied at the cleaning treatment before both the annealing and the lowtemperature annealing, and hence C1s/Cu2p exceeds the upper limit value.Further, since polishing is applied after the low temperature annealing,the area ratio of the fine crystal grains also exceeds the upper limitvalue and the oxide film adhesiveness retention temperature is furtherlow in comparison with Invention Example 5-1.

In Comparative Example 10-2, ethanol showing a weak detergency torolling oil and the like is used and also only dip cleaning is appliedat the cleaning treatment before both the annealing and the lowtemperature annealing, and hence C1s/Cu2p exceeds the upper limit valueand the oxide film adhesiveness retention temperature is low incomparison with Invention Example 10-1.

In Comparative Example 10-3, likewise ethanol showing a weak detergencyto rolling oil and the like is used and also only dip cleaning isapplied at the cleaning treatment before both the annealing and the lowtemperature annealing, and hence C1 s/Cu2p exceeds the upper limitvalue. Further, since polishing is applied after the low temperatureannealing, the area ratio of the fine crystal grains also exceeds theupper limit value and the oxide film adhesiveness retention temperatureis further low in comparison with Invention Example 10-1.

In Comparative Example 21-6, ethanol showing a weak detergency torolling oil and the like is used and also only dip cleaning is appliedat the cleaning treatment before both the annealing and the lowtemperature annealing, and hence C1s/Cu2p exceeds the upper limit valueand the oxide film adhesiveness retention temperature is low incomparison with Invention Example 21-1.

In Comparative Example 21-7, likewise ethanol showing a weak detergencyto rolling oil and the like is used and also only dip cleaning isapplied at the cleaning treatment before both the annealing and the lowtemperature annealing, and hence C1s/Cu2p exceeds the upper limit value.Further, since polishing is applied after low temperature annealing, thearea ratio of the fine crystal grains also exceeds the upper limit valueand the oxide film adhesiveness retention temperature is further low incomparison with Invention Example 21-1.

In Comparative Example 21-8, although hexane is applied at the cleaningtreatment before both the annealing and the low temperature annealingand C1s/Cu2p satisfies the stipulation of Claims, polishing is appliedafter the low temperature annealing, hence the area ratio of the finecrystal grains exceeds the upper limit value, and the oxide filmadhesiveness retention temperature is further low in comparison withInvention Example 21-1.

In Comparative Example 21-9, ethanol showing a weak detergency torolling oil and the like is used and also only dip cleaning is appliedat the cleaning treatment before both the annealing and the lowtemperature annealing, and hence C1s/Cu2p exceeds the upper limit value.Further, even though polishing is not applied after the low temperatureannealing, an abrasive paper of a small grit number (a large grain sizeof an abrasive) is used for the polishing after the annealing, hence thearea ratio of the fine crystal grains exceeds the upper limit value, andthe oxide film adhesiveness retention temperature is low in comparisonwith Invention Example 21-1.

A copper alloy plate according to the present invention has an excellentoxide film adhesiveness. Further, a copper alloy plate according to thepresent invention has a high strength and an appropriate bendingworkability necessary for a material for a lead frame. Consequently, acopper alloy plate according to the present invention is preferably usedas a material for a lead frame. Moreover, a copper alloy plate accordingto the present invention is preferably used for not only a lead frame ina semiconductor device but also various electric/electronic componentssuch as other semiconductor components, electric/electronic componentmaterials such as a printed circuit board, and mechanism components suchas switch parts, a bus bar, and a terminal/connector.

What is claimed is:
 1. A high-strength copper alloy plate excellent inoxide film adhesiveness, the copper alloy plate comprising Fe: 0.02-0.5%and P: 0.01-0.25% in mass % with the balance consisting of copper andunavoidable impurities and having the ratio Fe/P of Fe to P in mass %being 2.0 to 5.0, wherein: a ratio of the area of fine crystal grainsless than 0.5 μm in equivalent circle diameter to an observation areawhen a surface is observed by electron backscatter diffraction analysisis 0.90 or less; and the ratio C1s/Cu2p of a peak area of C1s to a peakarea of Cu2p on the surface by XPS analysis is 0.35 or less.
 2. Thehigh-strength copper alloy plate excellent in oxide film adhesivenessaccording to claim 1, the copper alloy plate further comprising Sn:0.005-3% in mass %.
 3. The high-strength copper alloy plate excellent inoxide film adhesiveness according to claim 1 or 2, the copper alloyplate further comprising Zn: 0.005-3% in mass %.
 4. The high-strengthcopper alloy plate excellent in oxide film adhesiveness according to anyone of claims 1 to 3, wherein: a tensile strength in the longitudinaldirection of the copper alloy plate is 500 MPa or more; and a percentageelongation after fracture in the longitudinal direction is 5% or more.5. The high-strength copper alloy plate excellent in oxide filmadhesiveness according to claim 1, wherein the XPS analysis is carriedout after alkali cathode electrolytic cleaning is applied.
 6. Thehigh-strength copper alloy plate excellent in oxide film adhesivenessaccording to claim 5, the copper alloy plate further comprising Sn:0.005-3% in mass %.
 7. The high-strength copper alloy plate excellent inoxide film adhesiveness according to claim 5 or 6, the copper alloyplate further comprising Zn: 0.005-3% in mass %.
 8. The high-strengthcopper alloy plate excellent in oxide film adhesiveness according to anyone of claims 5 to 7, wherein: a tensile strength in the longitudinaldirection of the copper alloy plate is 500 MPa or more; and a percentageelongation after fracture in the longitudinal direction is 5% or more.